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Commit 6a479079 authored by Ben Hutchings's avatar Ben Hutchings Committed by Jesse Barnes
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PCI: Add pci_clear_master() as opposite of pci_set_master() 



During an online device reset it may be useful to disable bus-mastering.
pci_disable_device() does that, and far more besides, so is not suitable
for an online reset.

Add pci_clear_master() which does just this.

Signed-off-by: default avatarBen Hutchings <bhutchings@solarflare.com>
Reviewed-by: default avatarMatthew Wilcox <willy@linux.intel.com>
Signed-off-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
parent b8d9cb2a

Documentation/PCI/pci.txt

+2 −1
Original line number Diff line number Diff line
@@ -294,7 +294,8 @@ NOTE: pci_enable_device() can fail! Check the return value. 


pci_set_master() will enable DMA by setting the bus master bit

in the PCI_COMMAND register. It also fixes the latency timer value if

it's set to something bogus by the BIOS.

it's set to something bogus by the BIOS.  pci_clear_master() will

disable DMA by clearing the bus master bit.



If the PCI device can use the PCI Memory-Write-Invalidate transaction,

call pci_set_mwi().  This enables the PCI_COMMAND bit for Mem-Wr-Inval

drivers/pci/pci.c

+28 −11
Original line number Diff line number Diff line
@@ -1667,6 +1667,22 @@ int pci_request_regions_exclusive(struct pci_dev *pdev, const char *res_name) 
					((1 << 6) - 1), res_name);

}



static void __pci_set_master(struct pci_dev *dev, bool enable)

{

	u16 old_cmd, cmd;



	pci_read_config_word(dev, PCI_COMMAND, &old_cmd);

	if (enable)

		cmd = old_cmd | PCI_COMMAND_MASTER;

	else

		cmd = old_cmd & ~PCI_COMMAND_MASTER;

	if (cmd != old_cmd) {

		dev_dbg(&dev->dev, "%s bus mastering\n",

			enable ? "enabling" : "disabling");

		pci_write_config_word(dev, PCI_COMMAND, cmd);

	}

	dev->is_busmaster = enable;

}



/**

 * pci_set_master - enables bus-mastering for device dev
@@ -1675,21 +1691,21 @@ int pci_request_regions_exclusive(struct pci_dev *pdev, const char *res_name) 
 * Enables bus-mastering on the device and calls pcibios_set_master()

 * to do the needed arch specific settings.

 */

void

pci_set_master(struct pci_dev *dev)

void pci_set_master(struct pci_dev *dev)

{

	u16 cmd;



	pci_read_config_word(dev, PCI_COMMAND, &cmd);

	if (! (cmd & PCI_COMMAND_MASTER)) {

		dev_dbg(&dev->dev, "enabling bus mastering\n");

		cmd |= PCI_COMMAND_MASTER;

		pci_write_config_word(dev, PCI_COMMAND, cmd);

	}

	dev->is_busmaster = 1;

	__pci_set_master(dev, true);

	pcibios_set_master(dev);

}



/**

 * pci_clear_master - disables bus-mastering for device dev

 * @dev: the PCI device to disable

 */

void pci_clear_master(struct pci_dev *dev)

{

	__pci_set_master(dev, false);

}



#ifdef PCI_DISABLE_MWI

int pci_set_mwi(struct pci_dev *dev)

{
@@ -2346,6 +2362,7 @@ EXPORT_SYMBOL(pci_release_selected_regions); 
EXPORT_SYMBOL(pci_request_selected_regions);

EXPORT_SYMBOL(pci_request_selected_regions_exclusive);

EXPORT_SYMBOL(pci_set_master);

EXPORT_SYMBOL(pci_clear_master);

EXPORT_SYMBOL(pci_set_mwi);

EXPORT_SYMBOL(pci_try_set_mwi);

EXPORT_SYMBOL(pci_clear_mwi);

include/linux/pci.h

+1 −0
Original line number Diff line number Diff line
@@ -642,6 +642,7 @@ static inline int pci_is_managed(struct pci_dev *pdev) 


void pci_disable_device(struct pci_dev *dev);

void pci_set_master(struct pci_dev *dev);

void pci_clear_master(struct pci_dev *dev);

int pci_set_pcie_reset_state(struct pci_dev *dev, enum pcie_reset_state state);

#define HAVE_PCI_SET_MWI

int __must_check pci_set_mwi(struct pci_dev *dev);